Referring to FIG. 1, for glider winch launch operations represented by 100, the winch is positioned on one end of a runway or field and the glider at the opposite end. Up to 6,000 feet of towline is pulled from the winch drum and towed to the end of the runway where the glider is located. The towline is then attached to the glider via a special tow hook. To launch the glider, the towline is reeled back onto the winch drum at line speeds up to 80 MPH. (Like reeling in a fish with a fishing reel at very high speed). The winch accelerates the glider to flying speed. The glider lifts off and rapidly climbs. The glider can reach altitudes of up to 3,000 feet above ground. At the top of the climb, usually directly above the winch, the glider releases and is free to search for thermals or if training, maneuver and return to the airfield for landing. After the glider releases the towline, the winch operator retracts the remaining towline back to the winch by continuing to wind it onto the drum. The towline has a small parachute on the glider end that prevents it from falling too fast and touching the ground before it is fully retracted. The launch is completed after release of the glider and the towline is fully retracted onto the drum. The process is repeated by towing the glider end of the towline back to the takeoff end of the runway for the next launch.
With reference to FIGS. 2 and 3, the current state of the art glider launch winch 101 is a single purpose machine that is normally constructed on a steel chassis, weighs a minimum of 5,000 pounds, has a high horsepower automotive, truck or crate engine, a three-speed automatic transmission, and a modified automotive rear axle onto which a large cable drum has been bolted in place of one of the normal driven wheels.
The winch drum 103 on current state of the art machines is usually mounted high enough on the chassis so the cable is wound onto the drum at the bottom thru a fairlead/guillotine mechanism (commercially supplied). Most state of the art winches are equipped with a complicated level wind system consisting of a jack screw or some other reciprocating device, a guide tube and rope rollers. The complex level wind system guides the cable or rope onto the drum in uniform layers. A guillotine is used to cut the towline in case of emergency. The current state of the art winch chassis is either built as a dual or single axle heavy trailer requiring a fairly large tow vehicle or is mounted on the back of a one ton truck 105. The current state of the art winch has dedicated fuel, electrical, cooling, exhaust and braking systems and, if mounted on a truck, does not share any of the truck ancillary power train systems. The winch is operated from what is normally a single seat safety cage 107 constructed of steel with a wire mesh safety grate for windshield and side windows and specially designed hand controls for the engine, transmission, and winch drum brake.
The current state of the art winch is controlled by operator feel with no performance input to the operator except for engine rpm and visual sight of the glider pitch and climb angle which are used as an indication of glider climb. Many current winches are underpowered so the operator simply applies full power and lets the glider pilot control the speed and climb rate by raising and lowering the pitch attitude of the glider. In modern times, many winch operations are replacing cable or wire with composite rope, creating other problems with the current winches, specifically structural failures in the drum due to the compression of the rope as it winds onto the drum under tension. On the current state of the art winch, the operator cab/cage usually faces toward the rear of the trailer or truck and the glider is pulled toward the rear of the winch platform. The current state of the art winch machine is mechanically complex and very expensive to build, completely lacks useful performance input to the driver, and can require considerable skill to operate in dynamic launch situations.